Microphones are typically constructed of two main components: Micro-Electro-Mechanical System (MEMS) devices that receive and convert incoming sound into electrical signals, and Application Specific Integrated Circuits (ASICs) that take the electrical signal from the MEMS device and perform post processing on the signal and/or buffering the signal for the following circuit stages in a larger electronic environment. The following circuit stages may be disposed in cellular phones, personal computers, or tablets to mention a few examples.
However, these previous microphones have limits as to how much signal the microphone can take before distorting the incoming signal. These distortions come from both the MEMS device and the ASIC and they are typically independent of each other.
Signal distortion in the ASIC generally happens when the input and/or the output electrical signal is too large a magnitude. A general way to control the input distortion is to have a circuit to clamp/soft clip the signal. This is to ensure that the signal will not be distorted in an abrupt and undesirable way but in a controlled way.
Previous clipping circuits sometimes used diodes. However, the problem with these previous circuits was that the diode had a very large temperature coefficient. This caused different clipping points to occur at different temperature.
The problems of previous approaches have resulted in user dissatisfaction with these previous approaches.
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